The role of ultrafine particles (UFPs) from a human health perspective is increasingly being recognized, and the interaction of these particles with their environment is dependent on, among other parameters, their size and number concentration. Size distribution measurements of ultrafine particles can be made using commercially available scanning electrical mobility spectrometers (SEMS). The scanning electrical mobility spectrometer technique uses a differential mobility analyzer (DMA) to classify particles based on their electrical mobility, and the concentration of the classified particles is typically measured using a condensation particle counter (CPC). In scanning electrical mobility spectrometer instruments, the voltage required for particle classification is exponentially varied to obtain size distributions in a relatively short time (˜5 minutes or less). Faster size distribution measurements are possible by combining the electrical-mobility classification technique with an electrometer detector array. The availability of commercial instruments has made ambient ultrafine particles measurements possible in near real-time and at high size resolution.
Accurate estimation of human health effect of ultrafine particles requires size distribution measurements considering their spatial and temporal variability. Such measurements require the deployment of instruments over a large number of sites or on a mobile platform, but the large cost, size, and power requirements of the existing instruments make such deployments difficult. Existing portable instruments provide a measure of ultrafine number concentration, but no sizing information, or provide inefficient size information.
Accordingly, there is a continued need in the art for systems and methods that facilitate real-time, size-resolved ultrafine particles measurements.